Journal of Mechanical Science and Technology最新文献

Forging dies, which are crucial for manufacturing automobile tripod housings, are frequently replaced owing to their extensive use under challenging conditions, leading to the disposal of many components and increasing manufacturing costs. The development of repair and remanufacturing technologies for high-hardness forging dies is a challenging. This study explores the on-site repair of tripod forging dies using wire arc directed energy deposition (arc-DED), assesses the hardness and tensile properties of remanufactured components, and compares them with the specified forging die requirements for on-site usability. A validated novel slicer is employed in remanufacturing experiments on a 9.8 % Cr die steel tripod-forging die. Results show the effectiveness of arc-DED in remanufacturing, surpassing the specified requirements by at least 111 HV and 61 MPa in hardness and tensile strength, respectively. Thus, this study presents a promising approach to reduce the manufacturing costs and environmental impact associated with the forging-die-component disposal.

This paper reviews the recent advances on the combination of component mode synthesis and model order reduction for geometrically nonlinear analysis, focusing on fixed-interface substructures and non-intrusive reduced-order models. These approaches offer significant potential for engineering applications by enabling accurate mechanical behavior prediction without detailed geometric and material information. Additionally, they facilitate safe sharing and collaboration between companies, reducing design times and production costs while also offering computational efficiency. However, challenges remain, indicating the need for future improvements in this area.

The instability of the increasingly important photovoltaic (PV) electricity generation in Korea due to a dependence on meteorological conditions is an emerging problem. In this study, we examined the influence of various meteorological conditions on the prediction accuracy of PV generation and module temperature. The predictions were based on weather data acquired from the Korea Meteorological Administration and compared with actual PV generation data from the Dangjin coal yard PV power facility. The results were analyzed on the basis of meteorological conditions, insolation, ambient temperature, and wind velocity.

The calculation of contact strength and stress of involute beveloid gears is difficult, and existing analysis methods encounter serious problems, such as long calculation time and poor accuracy, seriously affecting the promotion and development of these gears. To solve this technical problem, the geometric structure of involute beveloid gears is considered using the Hertz formula. In addition, the calculation methods for parameters, such as the contact ratio, contact ratio coefficient, and pitch cone angle coefficient, are determined. A Hertz contact model and a fractal contact model for involute beveloid gears were established using fractal theory, and the distribution law of contact stress was obtained. On this basis, a comparative analysis was conducted on the tooth surface contact stress obtained from the Hertz contact model, fractal contact model, and finite element model. The finite element analysis proves that the Hertz contact stress calculation formula and fractal contact model for involute beveloid gears established in this article have high accuracy, and can precisely reflect the actual contact stress value of the tooth surface.

This paper presents a comprehensive investigation on optimum layer thickness and fiber orientations of laminated composite plates against buckling under complex loading conditions by using a new optimization procedure that effectively utilizes computational efforts. In this proposed procedure, a finite element model of the laminated composite plates is developed for the buckling analysis and the interior point optimization procedure is used to maximize the buckling coefficient, aiming to determine the optimum values of fiber orientation angles and thickness. In optimization scenarios, the laminated composite plates are subjected to single and complex loading conditions, including compression, shear, bending and a combination of two or more of these loading types. The computational performance of the proposed optimization procedure is evaluated to investigate and present the effect of various factors including the number of layers, length-to-thickness ratios, aspect ratios, and boundary conditions on the optimum buckling analysis.

To solve the problem that the surface of conventional CeO₂ abrasive tools tends to glaze during the grinding process, water-resistant aluminum nitride powder (A/S powder) is added into abrasive tools to improve the self-sharpening ability. The effect of acetic acid content and sintering temperature on the water resistance of A/S powder is studied. The porosity, pre-grinding and mechanical properties of abrasive tools with different A/S powder content are tested. It is found that when the mixed A/S powder content is 9 wt%, there is no obvious glaze layer on the surface of abrasive tools, and the material removal rate is the highest. The result of grinding experiment shows that the glazing phenomenon is ameliorated and the surface roughness R_a and the flatness PV of quartz glass reaches 1.876 nm and 1.651 µm after the chemical mechanical polishing (CMP).

Performance of rotary ultrasonic machining (RUM) system greatly influences by appropriate design of ultrasonic horn. Ultrasonic stepped horn gives high amplitude of vibration and better cutting efficiency but design and integration of horn with RUM system is highly intricate. Therefore, systematic study on design and implementation of ultrasonic stepped horn was needed in order to achieve better efficiency of RUM process. This paper focuses on design aspects of ultrasonic stepped horn by theoretical, FE simulations and modeling techniques. The designed horn was integrated with RUM system, performance was measured in terms of ultrasonic resonant frequency through FE simulations and modeling on ANSYS workbench. Finally, fabricated ultrasonic stepped horn was validated by performing experiments on rotary ultrasonic machine tool for Nomex honeycomb composites (NHCs). FE simulations and experimental results prove that the designed ultrasonic stepped horn achieves reasonable vibration amplitude at desired resonant frequency to perform RUM process on NHCs materials.

This study establishes an empirical model for a four-flute cylindrical helical end mill, utilizing orthogonal cutting tests on a Ti-6Al-4V block as the machining workpiece. The reliability of the model was confirmed through a titanium alloy side milling experiment. Results demonstrate that the empirical index model for predicting the main cutting force error falls within the range of 4.19 %–10.0 %, providing an effective tool for cutting force prediction. The specific influence distribution trends of cutting parameters, including milling speed, feed per tooth, and depth of cut, on the cutting force through two-step milling of profile walled surface of titanium alloy were analyzed. The results reveal that the milling force in the first step exhibits a discernible upward trend with the increase of feed per tooth and radial depth of cut. Among the cutting parameters employed in the first step, the cutting speed exerts the most significant influence on the cutting force in the second step.

Currently, with the advancement of dual-clutch transmission (DCT) control systems and vehicle performance, it is necessary to develop better objective evaluation methods for DCT vehicles. The starting process is a critical element affecting the driving and riding experience of DCT vehicles. Therefore, it is crucial to establish and improve a starting process evaluation model for the objective evaluation to DCT vehicles and optimization to DCT control strategies. This paper proposes a new method to evaluate the DCT vehicle starting process objectively. The method analyzes and models the time-series signals of the driving data using the LSTM neural network and uses the attention mechanism to improve the evaluation performance and enhance the interpretability of the evaluation results. Taking the dynamic performance evaluation as an example, the evaluation results indicate that the proposed model is better than the conventional methods, showing notable efficacy and preponderance.

Due to the increase in renewable power generation sources, flexible operation is being required for large-capacity coal-fired power plants. Fatigue needs to be considered because the possibility of fatigue damage to equipment increases compared with rated operation. Existing studies qualitatively analyzed the impact on power generation facilities, and quantitative comparison studies were not conducted. Accordingly, this study comparatively analyzed the impact of flexible operation methods on the lifetime of boiler headers. Finite element analysis models were created to analyze stress in transient operation conditions, and fatigue rupture life was derived using fatigue test data from previous research. Then, as a result of assessing the fatigue life according to design criteria, the low load operation mode was confirmed to have a fatigue life 2.57 to 4.61 times longer than the start & stop mode. This study is intended to provide technical information for decision-making on flexible operation methods of power plants.